Einasto Profiles and the Dark Matter Power Spectrum

Abstract

We study the mass accretion histories (MAHs) and density profiles of dark matter halos using N-body simulations of self-similar gravitational clustering from scale-free power spectra, $P(k)\propto k^n$. We pay particular attention to the density profile curvature, which we characterize using the shape parameter, $\alpha$, of an Einasto profile. In agreement with previous findings our results suggest that, despite vast differences in their MAHs, the density profiles of virialized halos are remarkably alike. Nonetheless, clear departures from self-similarity are evident: for a given spectral index, $\alpha$ increases slightly but systematically with "peak height", $\nu \equiv {\delta }_{sc}/\sigma (M,z)$, regardless of mass or redshift. More importantly, however, the "$\alpha -\nu$" relation depends on $n$: the steeper the initial power spectrum, the more gradual the curvature of both the mean MAHs and mean density profiles. These results are consistent with previous findings connecting the shapes of halo mass profiles and MAHs and imply that dark matter halos are not structurally self-similar but, through the merger history, retain a memory of the linear density field from which they form.

MNRAS letters, accepted

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Cited by in corpus (5)

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• Connecting the structure of dark matter haloes to the primordial power spectrum
• Halo concentrations from extended Press-Schechter merger histories
• The cosmology dependence of the concentration-mass-redshift relation
• A dynamics-based density profile for dark haloes. I. Algorithm and basic results